Mesenchymal stem cells conditioned media-chitosan nanoparticles against clinical carbapenem-resistant Acinetobacter...

The objective of the present study was to assess the efficiency of stem cell-derived conditioned media (MSC_supCM) encapsulation in chitosan nanoparticles in combating carbapenem-resistant Acinetobacter baumannii (CRAB) bacteria, with a focus on the inhibition of bacterial growth and the prevention of biofilm formation.

The cytotoxic properties of nanostructures were investigated utilizing the A549 cell line as the model system. The antibacterial efficacy of the nanostructures was evaluated through the implementation of the broth micro-dilution technique. Furthermore, the quantification of anti-biofilm activity was conducted by employing colorimetric crystal violet staining assays. To further investigate the effects on biofilm formation, the gene expression levels of two crucial biofilm-associated proteins-Bap and ompA-were measured in CRAB isolates treated with these nanoconstructs using quantitative real-time PCR (qRT-PCR).

MSC_supCM was found to be negative for CD34 and CD45 markers, while it expressed CD73 and CD44 markers. The majority of MSC_supCM-CsNPs exhibited a mean particle size of 105.23 ± 0.308 nm, displaying suitable surface charge (6.23 ± 0.13 mV) and semi-spherical SEM morphology. The A549 cells showed 90 % viability after treatment with MSC_supCM-CsNPs (625 μg/ml). The entrapment efficiency of nanostructure was determined to be 70 % ± 3.26. The MSC_supCM-CsNPs revealed significant antibacterial/antibiofilm effectiveness compared to MSC_supCM, and CsNPs individually. Moreover, checkerboard results revealed significant synergistic effects of Imipenem and fabricated MSC_supCM-CsNPs against CRAB isolates (FICI = 0.45). MSC_supCM-CsNPs demonstrated a substantial reduction in biofilm formation of A. baumannii (Reduction Rate: 70.71 %) and A. baumannii + K. pneumoniae mixed cultures (Reduction Rate: 30.86 %). The MSCsupCM-CsNPs demonstrated a significant decrease in genes expression in comparison with MSCsupCM alone. Specifically, MSC_supCM-CsNPs showed a significant decrease in Bap and ompA gene expressions by 4.90 ± 0.06 and 10.52 ± 0.06-fold, respectively.

In conclusion, MSC_supCM-CsNPs presented a novel and highly effective therapeutic nanostructure for combating CRAB strains, exhibiting the synergistic activity of its two components and efficiently addressing the challenge of biofilm formation. The MSCsupCM-CsNPs, as a nanomedicine, offer a notable advantage, including the avoidance of antimicrobial resistance development, rendering it a promising therapeutic modality for the effective management of CRAB strains. The exploration of the synergistic antimicrobial potential of MSC_supCM-CsNPs in combination with other antibiotics has the potential to significantly enhance our therapeutic options for combating various pathogens.